We are thinking about installing the paid version of softaculous on our servers, however with the free version all the scripts seem to install in English, even scripts like dotclear or prestashop that are French scripts don't seem to be able to be installed in French.

With the paid version will our users be able to choose each script's install language ? Or at least will we be able to choose the default language.

For a lot of these scripts it's just a value that needs changing to fr-fr or something similar in the database.

With the paid version will our users be able to choose each script's
install language ? Or at least will we be able to choose the default
language.

Yes for some scripts one can select the language in the installation form.
But if you are interested in french language, at the moment only 9 scripts can be installed in french, though a lot of scripts have french translations.
Here is the list:
Wordpress, pivotX, phpBB, myBB, Dokuwiki, Advanced Poll, Piwik, Prestashop, SimpleInvoices.
I think french instal of famous scripts such as Joomla, drupal, coppermine etc.. could be added.

We have a bigger team now and we try to provide support as soon as possible.
To get faster support you should open a Support ticket:
http://www.softaculous.com/support/Also we have added the languages in many popular scripts. We are adding the languages in many more scripts. If you need language in any script let us know we will add it if possible.

Spanish Language is already available in Prestashop. We have also added spanish in joomla. Spanish for joomla 1.5 is not possible because the translation package is not available. We will try to add it in Drupal and Opencart.